void main() {
  int a = 10;
  int b = 5;
  b ??= 10;
  print(b);

  a += 2;
  print(a);
  a -= b;
  print(a);

  a *= b;
  a ~/ b;
  a %= b;

  String str;
  str ??= "hello";
  print(str);
}
